Comment 26 for bug 1518597

OK, major progress in isolating this issue, at least the root cause. Culprit is java and the fact that it now creates thousands of shared memory segments, for some reason (I am not running any java app I have not been running for months or years but I did rebuild one using the latest jdk). The messed up display issue arises when all shmem segments are busy. All of them have a zero key, some of them claim to have 1 and other 2 processes attached. Most but not all of them have the same size:

$ ipcs -m
...
0x00000000 86018571 chrisb 600 42864 1 dest
0x00000000 86051340 chrisb 600 91200 1 dest
0x00000000 86084109 chrisb 600 91200 1 dest
0x00000000 86149646 chrisb 600 42864 1 dest
0x00000000 86182415 chrisb 600 42864 1 dest
0x00000000 86215184 chrisb 600 236400 1 dest
...
0x00000000 135040993 chrisb 600 1690076 1 dest
0x00000000 135073762 chrisb 600 1690076 1 dest
0x00000000 135106531 chrisb 600 1690076 1 dest
0x00000000 135139300 chrisb 600 1690076 1 dest
0x00000000 135172069 chrisb 600 1690076 1 dest
0x00000000 135204838 chrisb 600 1690076 1 dest
0x00000000 135237607 chrisb 600 1690076 1 dest
0x00000000 135270376 chrisb 600 1690076 1 dest
0x00000000 135303145 chrisb 600 1690076 1 dest
0x00000000 135335914 chrisb 600 1690076 1 dest
0x00000000 135368683 chrisb 600 1690076 1 dest
0x00000000 135401452 chrisb 600 1690076 1 dest
0x00000000 135434221 chrisb 600 1690076 1 dest
0x00000000 135466990 chrisb 600 1690076 1 dest
0x00000000 135499759 chrisb 600 1690076 1 dest
0x00000000 135532528 chrisb 600 1690076 1 dest
0x00000000 135565297 chrisb 600 1690076 1 dest
0x00000000 135598066 chrisb 600 1690076 1 dest
0x00000000 135630835 chrisb 600 1690076 1 dest
0x00000000 135663604 chrisb 600 1690076 1 dest
0x00000000 135696373 chrisb 600 1690076 1 dest
0x00000000 135729142 chrisb 600 1690076 1 dest
0x00000000 135761911 chrisb 600 1690076 1 dest
0x00000000 135794680 chrisb 600 1690076 1 dest
0x00000000 135827449 chrisb 600 1690076 1 dest
0x00000000 135860218 chrisb 600 1690076 1 dest
0x00000000 135892987 chrisb 600 1690076 1 dest
0x00000000 135925756 chrisb 600 1690076 1 dest
0x00000000 135958525 chrisb 600 1690076 1 dest
0x00000000 135991294 chrisb 600 1690076 1 dest
0x00000000 136024063 chrisb 600 1690076 1 dest
...

$ ipcs -ml

------ Shared Memory Limits --------
max number of segments = 4096
max seg size (kbytes) = 32768
max total shared memory (kbytes) = 8388608
min seg size (bytes) = 1

When 'ipcs -m | wc -l' shows 4100 lines, the display messes up. Killing the java processes frees up all the shmem segments.

$ ipcs -m | wc -l
26

Overlap issues go away.